According to WHO data, psychiatric disorders are considered to be the second between the seven leading global health problems in the world today (1). Depression is a common disorder, widely distributed in the population with 16.2% prevalence and is associated with substantial symptom severity and role impairment (2). Seasonal Affective Disorder (SAD) is also common in certain areas of the world, with prevalence rates increasing with latitude: about 10% in Alaska and Canada (3,4), between 5.6-10.7% in UK (5), 8.9% in Central Europe (6) and only 3.7-6.6% in Turkey (7). Another major medical problem of the western civilization is Binge Eating Disorder. 6% of women population of the world will suffer from this eating disorder sometime during their life. (8). Sleep disorders as insomnia and sleep schedule disorders affect as much as 20% of the adult population and is increasing with age (9). Light Therapy is an evidence based medical noninvasive therapy that has been recently evaluated by a larged review study (10) and considered as an “effective non-drug treatment” for depression and many other troublesome medical problems as listed above. The State of the art of the Broad Spectrum Bright Light Therapy (BLT) is well established in the scientific literature (235 published studies) from 1984 (11) until today. It is used to treat seasonal (12, 13) and nonseasonal depression (14, 15), binge eating (16,17,18) and sleep and circadian rhythm disorders (19,20), including sleep problems of the demented patient (21, 22, 23, 24). Because of its minimal side effects profile (25, 26, 27), BLT has been successfully used in antepartum depression (28, 29), postpartum depression (30) and premenstrual dysphoric disorder (31, 32). The Canadian Psychiatric Association Clinical Guidelines (33) considers light therapy as a first line treatment in seasonal affective disorder. BLT implies the use of a Light Box (34) that uses fluorescent or neon light sources capable of producing wide/broad-spectrum white light between 2500-10000 lux. The Light Boxes usually filter the UV light (below 400 nm). The therapy consists of early morning exposure for about 30-60 minutes every day. An alternative to Light Box is the Light Visor, a small light device mounted on the head that produces 2000 lux bright light directly to the eyes (35). U.S. Pat. No. 6,875,225 discloses a light therapy device capable of generating 2,500 lux to 7,500 lux at 12 inches.
The biologic mechanism of light therapy involves the activation via optic pathways of the suprachiasmatic nucleus of the hypothalamus, inhibition of the melatonin production by the pineal gland and increase of the central serotonin level in the limbic system. (36). Another well-studied light therapy is Dawn/Dusk Simulation (DS)(37, 38). This therapy is acting on the melatonin cycle and is based on gradual increases of light while the patient is asleep, until a maximum brightness of 400 lux is achieved, thus mimicking the natural sunrise or sunset. According to some consistent studies (38), DS is as effective as BLT, but have a better compliance because it works while the patient is steel asleep. The existing dawn simulators are using bulbs capable of gradually (30-60 minutes) increasing the light to a maximum 400 lux only. Another well recognized non-pharmacologic therapy for depression is Sleep Deprivation (Wake Therapy). About 40-60% of the depressive symptoms improve after one night of sleep deprivation or after partial sleep deprivation of the second part of the night (39). Combined sleep deprivation and light therapy have been described in the literature (40,41,42), and considered to be superior to each therapy alone. Color Light Therapy is actually used as a traditional oriental medicine (acupuncture, ayurveda) (43).
All existing light devices have many limitations: The compliance of the patients using Light Boxes may be problematic because the treatment must be followed every day at early morning hours, while the patient is fully awake and the distance and the position of the device must be controlled. All these parameters are important for the efficacy of the treatment, but they depend on the cooperation with the patient and his understanding of the method. Light Visors are considered less effective than Light Boxes, the light brightness is of only 2000 lux but very close to the eyes, thus provoking unpleasant eye irritation. The dawn simulators are based on a different light therapy method (simulating the natural dawn) and have a better compliance because it works while the patient is asleep, but the spectrum and brightness are limited (e.g. maximum 400 lux), which are not enough for a true BLT. Wake therapy is not a device but a method and is not actually used in the clinical practice because when used alone, its antidepressant effect is transient. Recently, some devices using specific colors of the spectrum (green, blue) has been considered as equivalent to BLT, but the research in this direction is still limited. For example, WO 2005/004948 discloses a method for modifying or resetting the circadian cycle using short wavelength light.
Novel, effective, evidence based non-drug treatments for depression, anxiety, eating and sleep disorder are important challenges of the third millennium for a number of reasons: (1) minimal side effects compared to medication (2) better compliance with non-drug treatments (3) no stigmatization (3) minimal risk for pregnant women (4) not affecting lactation in postpartum depressed women (4) minimal interaction with other medication in poli-medicated patients. For all these reasons, a new Light Therapy method that overcomes the limitations of the existing light therapy methods and devices is needed.